Just ran across a strange problem.
One user could not be contacted by other users even though their presence was good.
This user could initiate conversations, and then things worked normally.
logging revealed the following:
TL_INFO(TF_PROTOCOL) 0AAC.0F60::02/10/2009-00:06:40.517.0000cb04 (SIPStack,SIPAdminLog::TraceProtocolRecord:SIPAdminLog.cpp(122))$$begin_record
Start-Line: SIP/2.0 500 The server encountered an unexpected internal error
CSeq: 1 INVITE
Proxy-Authentication-Info: Kerberos rspauth="602306092A864886F71201020201011100FFFFFFFF5A639D1C74445CDE716249160B5E67D5", srand="99E853C4", snum="27", opaque="753DF002", qop="auth", targetname="sip/OCS1.domain.org", realm="SIP Communications Service"
Via: SIP/2.0/TLS 18.104.22.168:56634;ms-received-port=56634;ms-received-cid=1F9900
ms-diagnostics: 1;reason="Service Unavailable";source="OCS1.domain.org";AppUri="http://www.microsoft.com/LCS/ApiModule";reason="The application specified an invalid static forwarding url"
Resolution: removed a bogus entry in AD user object.
Telephones| IP Phones | Other
There was a text entry there rather than numeric.
Question: What is the mechanics of the UR stuffing this bogus value into somewhere that caused this failure? I doubt I will ever know.